Testing Fundamentals

Last Reviewed:2015-11-17

Unittest

unittest is the batteries-included test module in the Python standard library. Its API will be familiar to anyone who has used any of the JUnit/nUnit/CppUnit series of tools.

As of Python 2.7 unittest also includes its own test discovery mechanisms.

unittest in the standard library documentation

Doctest

The doctest module searches for pieces of text that look like interactive Python sessions in docstrings, and then executes those sessions to verify that they work exactly as shown.

Doctests have a different use case than proper unit tests: they are usually less detailed and don’t catch special cases or obscure regression bugs. They are useful as an expressive documentation of the main use cases of a module and its components. However, doctests should run automatically each time the full test suite runs.

py.test

py.test is a no-boilerplate alternative to Python’s standard unittest module.

Despite being a fully-featured and extensible test tool, it boasts a simple syntax. Creating a test suite is as easy as writing a module with a couple of functions and then running the py.test command

$ py.test
=========================== test session starts ============================
platform darwin -- Python 2.7.1 -- pytest-2.2.1
collecting ... collected 1 items

test_sample.py F

================================= FAILURES =================================
_______________________________ test_answer ________________________________

    def test_answer():
>       assert func(3) == 5
E       assert 4 == 5
E        +  where 4 = func(3)

test_sample.py:5: AssertionError
========================= 1 failed in 0.02 seconds =========================

is far less work than would be required for the equivalent functionality with the unittest module!

py.test

Nose2

nose2 is the next generation of nicer testing for Python, based on the plugins branch of unittest2. nose2 aims to improve on nose by:

• providing a better plugin api

• being easier for users to configure

• simplifying internal interfaces and processes

• supporting Python 2 and 3 from the same codebase, without translation

• encouraging greater community involvement in its development

  nose2

tox

tox is a tool for automating test environment management and testing against multiple interpreter configurations.

tox allows you to configure complicated multi-parameter test matrices via a simple ini-style configuration file.

tox

Unittest2

unittest2 is a backport of Python 2.7’s unittest module which has an improved API and better assertions over the one available in previous versions of Python.

If you’re using Python 2.6 or below, you can install it with pip

You may want to import the module under the name unittest to make porting code to newer versions of the module easier in the future.

This way if you ever switch to a newer Python version and no longer need the unittest2 module, you can simply change the import in your test module without the need to change any other code.

unittest2

mock

unittest.mock is a library for testing in Python. As of Python 3.3, it is available in the standard library.

It allows you to replace parts of your system under test with mock objects and make assertions about how they have been used.

mock